Q11.35P - Chemistry: Molecular Nature Of Matter And Change

Question

Use MO diagrams and the bond orders you obtain from them to answer: 

(a) Is  ${{\mathbf{O}}_2}^{-}$ stable? 

(b) Is   ${{\mathbf{O}}_2}^{-}$ paramagnetic? 

(c) What is the outer (valence) electron configuration of  ${{\mathbf{O}}_2}^{-}$ ?      

Step-by-Step Solution

Answer

Electrons in bonding orbitals stabilize they are between the nuclei. 

1. Yes,  ${{\mathbf{O}}_2}^{-}$ is stable.
2. No,  ${{\mathbf{O}}_2}^{-}$ is not diamagnetic.
3. The outer valence electron configuration of  ${{\mathbf{O}}_2}^{-}$ is sigma anti-bonding 2s orbital.

Step 1: Bonding

Bonding may be defined as the force of attraction between two or more atoms to form a compound. The molecule can have the same atom and a different atom.

The bonding can be formed by sharing or completing giving the electron from one atom to another.

 

When the electron is in pair in the valence shell it is called diamagnetic whereas the valence orbital having a single electron is called a paramagnetic atom.

Step 2: Stability

The Stability of the molecule depends upon the less energy and stability of the molecule formation. In this molecule  ${{\mathbf{O}}_2}^{-}$ , The Bond order of the molecule is more than zero which shows it is quite a stable molecule.

 

 $\begin{array}{l}\mathbf{Bond}\mathbf{ }\mathbf{Order}\mathbf{=}\frac{1}{2}\left[\mathbf{(}\mathbf{Electron}\mathbf{ }\mathbf{in}\mathbf{ }\mathbf{BMO}\mathbf{)}\mathbf{-}\mathbf{(}\mathbf{Electron}\mathbf{ }\mathbf{in}\mathbf{ }\mathbf{ABMO}\mathbf{)}\right]\\ \mathbf{Bond}\mathbf{ }\mathbf{Order}\mathbf{=}\frac{1}{2}\left[\mathbf{(}\mathbf{10}\mathbf{-}\mathbf{7}\mathbf{)}\right]\\ \mathbf{Bond}\mathbf{ }\mathbf{Order}\mathbf{=}\mathbf{1}\mathbf{.}\mathbf{5}\end{array}$

$\mathbf{BMO}\mathbf{=}\mathbf{Bonding}\mathbf{ }\mathbf{Molecular}\mathbf{ }\mathbf{Orbital}$

 

 $\mathbf{ABMO}\mathbf{=}\mathbf{Anti}\mathbf{-}\mathbf{Bonding}\mathbf{ }\mathbf{Molecular}\mathbf{ }\mathbf{Orbital}$

Step 3: Magnetic Character

The magnetic character of the molecule ${{\mathbf{O}}_2}^{-}$  is paramagnetic. There is a single electron in the valence shell of an atom.  

 The electronic configuration of Superoxide:

 $\mathbf{\sigma }\mathbf{1}{\mathbf{s}}^2{\mathbf{\sigma }}^{*}\mathbf{1}{\mathbf{s}}^2\mathbf{\sigma }\mathbf{2}{\mathbf{s}}^2{\mathbf{\sigma }}^{*}\mathbf{2}{\mathbf{s}}^2\mathbf{\sigma }\mathbf{2}{\mathbf{px}}^2\text{}\mathbf{\pi }\mathbf{2}{\mathbf{py}}^2\text{}\mathbf{\pi }\mathbf{2}{\mathbf{pz}}^2\text{}{\mathbf{\pi }}^{*}\mathbf{2}{\mathbf{py}}^2\text{}{\mathbf{\pi }}^{*}\mathbf{2}{\mathbf{pz}}^1$

Step 4: Molecular Orbital

The outer most valence orbital shell of the ${{\mathbf{O}}_2}^{-}$  is pi anti-bonding of 2p orbital. There is one extra electron than the oxygen molecule in ${{\mathbf{O}}_2}^{-}$ superoxide.